I think the 24 represents
passes defensed, which is a combination of interceptions and tipped passes.
Samuel has a history of this going back to college, where he's still the career leader there. And with the Pats, he led the team in passes defensed before this season also. Difference being, this season he caught more balls leading to his 10 interceptions, but in the past -- he only tipped (or dropped) them. Both Samuel and BB have referred to his improvement (sticky hands) as a major factor in his development.
BTW, when we talk about 'ball skills' pertaining to DB prospects, the "passes defensed" category is an important one to consider. BB has mentioned this quality on several occasions. Primarily means the DB is always around the ball and in position to make a play.
Thanks for posting this interesting tidbit.